The necessity of providing a juncture on a pipe that is professionally finished so that it can be fastened to an adjoining pipe with a defect-free weld has been appreciated for some time. In pipe lines, nuclear reactors, and the like, the necessity to provide junctures that are reliable and durable are of the utmost importance. Frequently, the working conditions associated with pipe machining equipment have been quite hostile either to the machine or to the machine operator. For example, in nuclear reactors the necessity for pipe replacements has been such that these types of maintenance procedures are quite frequently occurring and maintenance personnel may only work in an area that is radioactively hot for extremely short periods of time. Accordingly, the desirability of an apparatus for finishing pipes which once set up can proceed automatically, and can be initialized in a minimum amount of time has found increasing importance and acceptance in industry.
Prior art devices which have attempted to address these problems in the past include the following U.S. Pat. Nos.:
2,769,234--Young PA1 2,145,191--Pennington PA1 3,644,977--Valentine PA1 3,650,514--Stunkard PA1 3,942,248--Sherer et al. PA1 3,807,047--Sherer et al. PA1 3,744,356--Slator et al. PA1 3,875,831--Beauloye PA1 4,050,335--Gilmore PA1 3,762,246--Becker PA1 3,772,944--Becker
These references while generally being directed to pipe working machinery, neither contemplate nor provide for the advantages associated with the mechanism according to the instant application.
Specifically, it is to be noted that the prior art provides for a drive mechanism in which a rotating ring is provided with a circumferential ring gear that is totally exposed and open to the elements. Clearly, when a machining operation is to occur, particulate matter such as shavings and other enviromental contaminants can interfere with the motor drive mechanism as it relates to the ring gear and can therefore provide binding in the rotation to the detriment of the work. Additionally however the exposed ring gear provides a needless hazard for the operators of the machinery, and such a hazard can be substantially magnified when working in close quarters, or in other difficult conditions such as underwater cutting and especially in combustible areas.
Additionally, the prior art fails to provide for the mechanism according to the present invention in that the indexing mechanisms are not provided on the same face of the rotating implement as the cutting tool. This, of course, makes the set-up operation for pipe working somewhat more laborious. In addition, while some of the prior art devices attempt to provide mechanism which can accommodate pipes that are not perfectly round, the actual centering operation of these mechanisms is somewhat more laborious than that which is taught in the instant application. The clamping devices according to the present invention cause this lathe to operate accurately on hollow or solid stock having square, circular, or any other external geometric configuration.
Furthermore the unique overall structure of the lathe according to the present invention does work which heretofore required two different machines: that is to say the mechanism according to the present invention has the versatility to serve as both a vertical turret lathe and an engine lathe.